Motorized doors or gates (both terms being used herein as equivalent) comprising a shutter are commonly used to shut off openings, particularly in warehouses, supermarkets, or industrial halls. These shutters are often made up of large flexible tarpaulins the lateral edges of which comprising beads (1B) which slide in guiding rails (4) situated on each side of the opening that is to be closed. Alternatively, they can be made of rigid panels hinged to one another side by side or the shutter can be a rigid panel. Automatic doors are particularly useful when they are used to separate two spaces having different environmental conditions, such as temperature, relative humidity and the like, and more particularly to separate an indoor space from outdoor. Doors able to open and close at high speed are also known for these applications and are often referred to as “fast doors”.
One issue with motorized doors, particularly with fast doors due to their high closing speeds, is impacts with obstacles accidentally located within the closing trajectory of the shutter. Besides damaging the leading edge of the shutter and also disengage the bead of the shutter lateral edges from the guiding rail, the obstacle itself can be damaged. Considering that such obstacle can be a person, the danger in case of an impact of injuring said person is quite high and must be reduced. For this reason, strict norms have been imposed on motorized doors. For example, in order to comply with the European norm EN12453, the peak force of an impact with a body must not exceed the limit of 150 N during more than 5 s, and must not exceed the limit of 400 N during more than 0.75 s.
In order to meet these severe requirements, the leading edges of motorized doors are often equipped with damping elements, such as a lip made of a resilient material, or pneumatic absorbing pistons. For most doors, in particular fast doors, which have a high kinetic energy, such damping elements reduce the impact force in case of impact, but not sufficiently to meet the requirements of EN12453. Many doors are therefore additionally or alternatively provided with detection cells.
An accidental event detection cell can comprise contact detectors as disclosed for example in US2007/0261305. Alternatively, some detection cells are based on the comparison with a reference value of parameters such as the motor torque, motor energy consumption, or shutter closing speed, such as in U.S. Pat. No. 5,198,974. Such detection cells, however, identify the occurrence of an impact only after the leading edge has contacted the obstacle, which is of limited use for a person being hit by the leading edge of a closing shutter.
Since preventing is better than repairing, many motorized doors have been developed comprising (a) contactless detection cells suitable for detecting the presence of an obstacle within the closing trajectory of a shutter before an impact occurs, and (b) a control system programmed for implementing a safety function aimed at managing the accidental presence of obstacles, in particular by stopping the door in its travel when it encounters one and moving it away from the obstacle in order to allow the removal thereof.
Various types of such contactless detection cells are known in the art, such as in U.S. Pat. No. 7,034,686 disclosing a proximity detector provided with an antenna, which triggers a command to stop and reverse the closure of the vertical door when the magnetic field created by the antenna is disturbed by a foreign object. This system has the advantage of preventing an impact, but it has the drawback of lacking precision given that the magnetic field may radiate outside the closure plane and thus cause false alarms triggered by objects situated close to the door but not underneath it. Optical, ultrasonic and radar sensors are also available which are able to detect the presence of a foreign body within the trajectory of the shutter. A person skilled in the art therefore has a selection of detection cells to choose from for detecting an accidental event.
Once an obstacle has been detected, a safety function must be triggered. In particular, such safety function almost always includes stopping the closing motion of the shutter and sometimes comprises reversing the direction of the motion to re-open the shutter. For example, U.S. Pat. Nos. 7,034,682, 6,989,767, 5,198,974 and US2007/0261305 disclose safety systems for doors in which, as soon as an accidental event is detected, the motor stops, reverses its direction of rotation in order to open the door completely and stops definitively when the door is completely open. The door can be closed once again by manual intervention.
The detection cells and control systems of the art cannot identify the nature of an obstacle and would treat any identified object as an accidental obstacle. The shutter is closed when the leading edge contacts a distal transverse edge (for vertically top-down shutters, it generally corresponds to the floor). It is clear that the detection by the detection cells of the approaching distal transverse edge should not be treated as an accidental obstacle, triggering the stopping of the shutter. At the same time, the impact force between the leading edge and the distal transverse edge shall remain moderate. There are systems able to determine the instant position of the leading edge. For example, some systems count the number of revolutions of the motor to estimate the position of the leading edge. Though very simple, this system is not very reliable, at least when the shutter is a flexible shutter rolled up around a drum, because at each revolution of the drum, the length of shutter being delivered varies as a function of the diameter of the drum. A more sophisticated system uses optical sensors counting the number of specific markers provided at regular intervals on longitudinal edges of the shutter (transverse to the leading edge) which pass in front of said optical sensors. Such systems are much more reliable than the former one, but all doors are not necessarily provided with such systems, which cannot be added easily to a standard door. Furthermore, there are situations, wherein such position detection systems cannot be used satisfactorily.
For example, it is possible that a raised deck (e.g., the platform of a lorry) be momentarily installed across the door frame to serve as an upper transfer surface for moving goods from one side to the other of the door. In this case, the raised deck shall form a new “momentary distal transverse edge,” where the leading edge shall stop and contact in its closed configuration. A system determining the instant position of the leading edge will be of no use in this case because the CPU would be programmed to run the shutter in the closing direction until the original distal transverse edge, which is positioned further from the momentary distal transverse edge. The CPU would consider the raised deck detected by the detection cells as an accidental obstacle, triggering the stopping of the shutter and, possibly, the reversal of the shutter movement to re-open the shutter.
There therefore remains a need in the art for detection cells and a control system applied to motorized doors, which can distinguish between a body forming an accidental obstacle and a body forming a distal transverse edge defining the final position of the leading edge when the shutter is closed. The present invention provides a motorized door provided with detection cells and a control system (CPU), which avoids any impact of the leading edge of the shutter with a body with an impact force of more than 400 N as defined in EN12453. At the same time, the CPU is able to distinguish between an accidental obstacle and a distal transverse edge, regardless of the position of the latter, and to trigger different actions depending on the nature of the body. The detection cells and control system of the present invention can be implemented on any existing doors with little effort and low cost. This and other advantages of the present invention are presented in continuation.